Utterance of “GM crops” usually has the effect of inciting
anger in the public mind, while scientists shake their heads at public
misunderstanding.Although in
principle I strongly favor the development of GM crops if they’re used to make
agriculture more sustainable, the multinational companies that give us these
technologies have really botched the relationship with farmer and public.These companies can now only find camaraderie
with scientists, business folk, and lawyers.

Two recent papers have reported the benefits of one GM crop:
Bt cotton.The ‘Bt’ stands for Bacillus thuringiensis, a Firmicute bacterium capable of producing a crystal toxin that, upon ingestion, punches holes in the digestive
tracts of insects (and even some nematode worms).The gene encoding the Bt toxin (at least one form of it, there
is a diversity of toxins) has been added to the cotton genome so that the plant
can now express this toxin.The good
thing is that only insects that are feeding on the cotton will be exposed to
the toxin, thereby killing the cotton pests but not the surrounding populations
of beneficial insects.

Kathage and Qaim (PNAS 109: 11652; http://www.pnas.org/content/109/29/11652.full)
present data from Indian cotton farms that suggest overall cotton yield has
increased during their 6 years of monitoring, resulting in a larger profit for
individual farmers.This increase
in profit even accounts for the 2-3 fold higher cost of Bt cotton seed.This has been accompanied by an
increase in a measure of Indian living standards.

Lu et al.* (Nature 487: 362; http://www.nature.com/nature/journal/vaop/ncurrent/full/nature11153.html)
analyze how natural aphid populations, and their predators, are affected by Bt
cotton.The idea here is that
because Bt cotton has its own internal insecticide factory, there is no need
for spraying of external insecticides, and because spraying insecticides kill
beneficial insects too, planting Bt cotton results in recovery of natural
populations of insects that prey on the destructive Bt-resistant aphids.Lu et al. found that, indeed, natural
aphid predators increase in abundance and aphids decrease in abundance when Bt
cotton is planted (or if regular cotton is planted but no insecticide is
applied).

These studies both shine a bright light on the benefits of
GM technology.But questions
remain.Planting only one variety
of cotton (GM Bt cotton) around the world surely has consequences, from eliminating
locally adapted varieties of cotton to restricting the freedom of farmers.Furthermore, it is known that
resistance to Bt toxin can evolve readily in many populations of insect
pests.There are management
strategies to deal with this, where acres of non-Bt crops are planted to help maintain Bt-sensitive populations.But is this enough?How many years will Bt crops be a
viable option?As a scientist I
welcome the outcome of this experiment, but I also find gambling with agriculture a bit nerve wracking.Then I ask myself: what are the
alternative options?My mind comes
back to the original problem of explosive insect pests enabled by vast fields
of monoculture.

*My apologies for this not being open access.It was my goal to only blog about
research everyone could access.Inevitably, this goal will not always be achieved.